To ensure product safety, a power supply for a consumer electronic product needs to have output over-voltage protection (OVP) and short-circuit protection (SCP) to shut down the power supply circuitry in the event of abnormal operation. A traditional OVP circuit used with a floating converter circuit such as a floating buck converter uses differential detection. FIG. 1 illustrates such a circuit. Power supply 100 includes a differential detection circuit 102 across the positive and negative output terminals of floating buck converter 104 to sense output voltage. Once the differential output voltage is larger than the designed voltage, differential detection circuit 102 triggers control circuit 106 to shut down the converter. In this example, the differential detection circuit and/or the control circuit are specifically designed for the output voltage required of the floating buck converter.
A traditional SCP circuit used with the floating buck converter is more complicated. As shown in FIG. 2, circuit 200 includes differential amplifier 202 connected across a resistor RL in series with the load driven by floating buck converter 204. Amplifier 202 converts the sensing signal to a voltage signal which references control ground through resister RS. Once the load current rises above a designated level, the differential amplifier triggers control circuit 206. For a high voltage power supply output, the negative side voltage with reference to control ground is very high and an expensive differential amplifier with a high-voltage transistor must be used.